(a) Field of the Invention
The present invention relates to a method of preparing transparent resin of rubber-modified styrene copolymer with excellent transparency and impact resistance, specifically, to a method of preparing transparent resin of rubber-modified styrene copolymer with excellent transparency and impact resistance comprising graft-copolymerizing styrene monomer and (meth)acrylate monomer in the presence of block or random styrene-butadiene copolymer which has 30˜50% of styrene skeleton content and 20˜40 cp of 5% toluene solution viscosity at 25° C.
(b) Description of the Related Art
A rubber-modified thermoplastic styrene resin with improved impact resistance is obtained by graft copolymerization of styrene monomer in the presence of rubber polymer. However, due to rubber particles dispersed in resin, conventional rubber-modified styrene resin looses its transparency, this is one of the merits of styrene resin, leading to the limited application.
For example, European patent laid-open No.0703252, and Japanese patent laid-open Nos.Hei5-54484 and Hei4-180907 disclosed graft-coplymerization of styrene monomer and (meth)acrylate monomer in the presence of rubber polymer in order to provide rubber-modified styrene resin with transparency.
However, in the transparent rubber-modified styrene resin prepared by the methods described in the patents above, the shape of grafted-rubber particle has mainly salami structure and only occasionally, they show onion structure or core-shell structure. The shape of rubber particle is affected by viscosity, molecular weight, and content of styrene skeleton of rubbery polymer and depends on the stirring speed of reaction mixture and degree of graft. Generally transparent rubber-modified styrene resin having particle shape of salami structure has an excellent impact resistance, but it has poorer transparency than core-shell structure. Resin transparency is better for the smaller rubber particle, and the particle of core-shell structure is better than that of salami structure. Furthermore, rubber-modified styrene resin having core-shell structure is also known to have excellent gloss. However, it has remarkably poor impact resistance. Onion structure has medium impact resistance of salami structure and core-shell structure.
Japanese patent laid-open No.Hei10-72512 disclosed the art to obtain small particle size while using salami structure. However, it still has a problem of poor transparency.